Darcy O'Brien, a college professor and author of several fiction and nonfiction books, was in Europe last summer when he was urgently summoned back to New York by his publisher.

It seemed that there was a problem with his about-to-be published book, "Two of a Kind: The Hillside Stranglers," the first full-length account of the investigation and trial of the men who had terrorized Los Angeles in 1977 and 1978 with a series of brutal sex murders.

Advance copies of the book had made their way to Los Angeles. And now the publisher, New American Library, had letters complaining about certain passages and characterizations in it.

Objections by Lawyers

One letter was from Gerald Chaleff, the defense lawyer whom O'Brien had credited with making the Hillside Strangler case the longest criminal trial in U.S. history. Another was written by one of the country's leading libel litigators on behalf of Chaleff's co-counsel, Katherine Mader.

Even though the normal editing process was behind them and the book was in the final stages of printing, O'Brien hastened home to discuss the complaints with the publisher's lawyer.

What happened next illustrates a fundamental change in the book industry in recent years: Lawyers are playing an ever-increasing role in the editing of books.

When the book appeared in stores some months later, certain passages were missing and others were rewritten. Some changes were barely noticeable: in one instance, a single word replaced by another. In other places, entire paragraphs were altered or omitted.

Gone, for example, were unflattering descriptions of Mader, characterizing her as so "distastefully frank" that "no matter what she was talking about--sodomy, lunch--she always smiled, a small smile, short of a grin, but disconcerting because it seemed irrelevant, incongruous, like a sunbonnet on a crocodile."

Other Changes Made

And there were other changes--none of which are being discussed publicly, either by those who made the complaints or those involved in reediting the manuscript.

In making the changes, were the author and publisher responding to actual errors that had come to their attention late in the publishing process? Or were they capitulating, unnerved by an apparent threat of litigation from what were some of the country's heaviest legal guns?

In this particular case, those questions may never be fully answered. In a general way, however, such questions are being raised throughout the publishing industry today.

Many lawyers say the trend toward "vetting" or "lawyering" books is a good one. Attorneys, they argue, are simply protecting the rights of their clients--their right not to be defamed, their right to privacy, their right not to be exploited, their right to profit from publicity about their own life stories.

Yet, increasingly, scholars and writers are becoming disturbed by what they see as a major shift in book publishing standards. Publishing companies, their critics contend, are so afraid of litigation that they are allowing their legal departments to become offices of censorship.

While newspapers and broadcasters have long had to worry about potential litigation arising from what they say or print, publishers at many book companies believe that they have become particularly vulnerable in this regard in recent years.

One of the reasons, said R. Bruce Rich, an attorney for the Freedom to Read Committee of the Assn. of American Publishers, is that most courts have come to make a distinction between publishers who work under stringent deadlines and those who do not.

The courts, Rich said, seem to view book publishing as a "leisurely" process in which writers and editors have the time and resources to get things right; if they do not, they will be penalized.

What is more, publishers' lawyers say, it is not the so-called Hollywood "trash" books that are most vulnerable to lawsuits. Those books are generally seen for what they are: providers of cheap entertainment and free publicity. What has been subjected to the threat of litigation, the publishers say, are serious books about important subjects.

Litigation Mania

To some extent, what is happening in the publishing merely reflects the litigation mania that has seized 20th-Century America. But the problems facing publishers and writers come from a whole host of directions.

If they use real names and purport to tell a true story, they can be sued for invasion of privacy or libel.

If they change the names and say they are creating fiction, they can still be sued for libel.

If they make money from telling a true story, they can be sued for violation of property rights.

If they profit financially from telling a story about a crime, they can be sued for exploiting the rights of victims.